Within the ATP World Tour Rankings there are four categories of tournaments where players can get points for the rankings:
ATP 2000
Grand Slams : Australian Open, Roland Garros, Wimbledon, US Open*
ATP 1000
Masters : Cincinnati, Indian Wells, Madrid, Miami, Monte Carlo, Parijs, Rome, Shanghai, Montreal
ATP 500
ABN AMRO World Tennis Tournament, Acapulco, Barcelona, Basel, Beijing, Dubai, Hamburg, Tokio, Washington, Halle, Queen's Londen, Vienna en Rio de Janeiro
ATP 250
All other ATP World Tour tournaments, including for example the Ricoh Open
The stated number of points indicates how many points the winner of the tournament gets for his ATP World Tour Ranking.
* Grand Slams are not ATP events